WASHINGTON—The U.S. next week will impose an additional 10% tariff on imports from China over its role in the fentanyl trade, President Trump said.

The move, slated to take effect Tuesday, doubles up on the previous 10% of additional tariffs the president placed on Chinese products earlier this month.

In a Thursday post on his Truth Social platform, Trump also reinforced his threat to impose 25% tariffs on products from Canada and Mexico, saying America’s neighbors hadn’t done enough to curb drug smuggling to win another delay for those duties. The administration had postponed the Canada and Mexico tariffs for 30 days at the beginning of February to allow for negotiations.

“[T]he proposed TARIFFS scheduled to go into effect on MARCH FOURTH will, indeed, go into effect, as scheduled,” Trump said. “China will likewise be charged an additional 10% Tariff on that date.”

Updates to follow as news develops

Write to Gavin Bade at gavin.bade@wsj.com